A severe storm traveling at 60 mph will cover 30 miles in 30 minutes. This period of time is considered to be the ideal warning time for an individual in the path of a storm to take the necessary actions to insure their safety during severe weather conditions.
A radio atmospheric signal, or sferic, is a broadband electromagnetic impulse that is known to occur as a result of natural atmospheric lightning discharges. The radio frequency (RF) signal resulting from lightning is relatively strong and broad in spectrum. There are essentially three types of radio atmospheric signals (sferics). Cloud-to-ground is the most intense and dangerous form of sferic, commonly exhibiting RF signals between 1 kHz and several Mhz. Cloud-to-ground sferics comprise as little as 10% of the total electrical activity associated with severe weather and have been shown to have no correlation with tornadic activity (as shown by the studies conducted by NOAA such as the 1991 Beryl tropical storm over the Carolinas). Cloud-to-cloud and intracloud sferics are not visible during the day and comprise the majority of sferic activity in a storm. Intracloud sferics exhibit RF frequencies most commonly between 100 kHz and 10 MHz. Only infrequent and very intense intracloud discharges produce frequencies at or below 300 kHz. For sferic RF transmissions above 10 kHz, there is an inverse relation between sferic RF frequency and signal strength.
Researchers originally believed that lightning activity was responsible for tornado-genesis and for providing the energy necessary to maintain tornadic activity. Subsequent studies using sophisticated wide area lightning detection arrays (i.e., National Lightning Detection Network et al.) have shown that areas associated with tornadoes have little to no lightning activity and are actually called “lightning holes”. However, it has also been shown that electrical activity co-exists with funnel clouds in that numerous observations of luminous events, electrostatic discharges and unusual lightning displays, the smell of ozone, heat stressed vegetation, St. Elmo's fire, etc. have consistently been reported, photographed and documented. The descriptions and measurements of these events correlate with that of the behavior of plasma. Atmospheric plasma sferics associated with aurora activity, ball lightning (believed to be a stable form of a spheroid sferic plasma structure) and the Plasma Pulse Generator of tornadoes have been shown to exhibit sferic frequencies from 500 kHz to 5 MHz.
What is needed in the art is a system and method for detecting a severe storm or tornado using RF signals emitted by lightning and other electromagnetic phenomenon. Additionally, what is needed in the art is a system and method for providing adequate warning to individuals in the path of such a severe weather condition.